Abstract
Free radicals are involved in several normal biological processes in vivo . Free radicals are involved, in a controlled fashion, in many normal biochemical mechanisms in vivo but they can become highly reactive if not tightly controlled. If the controlling processes are overwhelmed, free radicals can become highly destructive to cells and tissues. Free radicals are also involved in the mechanism of action of certain enzymes, for example, the iron–sulphur enzyme ribonucleoside diphosphate reductase, and the heme enzymes cytochrome P-450 and prostaglandin synthase. The enzymic oxidation of arachidonic acid during eicosanoid biosynthesis is accompanied by the generation of hydroperoxides and formation of oxygen-derived free radicals. The actions of prostaglandin synthase and lipoxygenase operate through a mechanism involving free-radical intermediates. The peroxidase-catalyzed conversion of the hydroperoxide PGG2 to PGH2 during prostaglandin synthesis is considered to yield oxygen radicals, an active heme iron–oxygen ferryl species being formed during the peroxidase reaction.
Published Version
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